An energy harvesting technology corresponds to a field of harvesting energy from a peripheral environment, and is a technology for converting peripheral energy to electric energy usable for driving a circuit. The energy harvesting technology has a characteristic in that the technology enables a circuit to be operated without a battery or a charging of a battery by using separate power, so that the technology can be used as power or auxiliary power of various sensors and a communication device using the sensor, and an application scope thereof is considerably wide. The energy harvesting technology is also a future industry field capable of preserving a natural environment by efficiently re-using energy discarded in a peripheral area.
A method of harvesting energy from light of a natural environment by using a solar cell has been most widely known as the energy harvesting technology. However, the aforementioned method has very low energy efficiency obtainable under an indoor environment, such as a building, and demands a too large area to be applied to a small circuit device, so a field to which the method is applicable is limited. Recently, research on the harvesting of energy by various methods, such as a method of harvesting energy by using vibration or a temperature difference and a method of harvesting energy by receiving an electromagnetic signal by using an antenna having a size of [mm] is in progress.
In the meantime, lighting devices presently used in an indoor space have large power consumption in the amount of several tens of Watts for each device, and a part of power input to the lighting device is not converted to light, but is radiated as heat and an electromagnetic wave. Accordingly, large power can be harvested if the electromagnetic waves emitted from the lighting devices are used as an energy resource. A fluorescent light which has been the most widely used currently is classified into a magnetic ballast type and an electronic ballast type according to a driving method, and the magnetic ballast type emits an electromagnetic wave of a frequency of 60 Hz and the electronic ballast type emits an electromagnetic wave of a band of several tens of kHz according to a driving characteristic. However, in a case where the antenna type in the related art is used, there is a problem in that it is almost impossible to implement an antenna capable of absorbing an electromagnetic wave of such a low frequency band and harvest the emitted electromagnetic wave due to a spatial limitation.